This invention relates to a gating circuit for controlling a switching device employed in a deflection circuit.
Various deflection system designs have been utilized in television receivers. One design employing two bidirectional conducting switches and utilizing SCR's (thyristors) as part of the switches is disclosed in U.S. Pat. No. 3,452,244. In this type deflection system, a first SCR is employed for coupling a deflection winding to a source of energy during a trace interval of each deflection cycle and a commutating network including a second SCR is utilized for storing energy and for supplying the stored energy to the deflection winding during a commutation interval of each deflection cycle. The first SCR is commonly provided with gating voltage by means of a separate winding or tap of an input reactor coupling a source of direct current to the second SCR and the commutating network.
Various regulator system designs have been utilized in conjunction with the above-described deflection system to provide for uniform high voltage production as well as uniform picture width with varying line voltage and kinescope beam current conditions.
One type regulator system design alters the amount of energy stored in the commutating network between commutating intervals. A regulator design of this type may utilize a regulating SCR and diode for coupling the input reactor to the source of B+. With this type regulator the current is interrupted such that a notch, the width of which depends upon the regulation requirements, is created in the current supplied through the reactor and which notch shows up in the voltage waveform developed on the separate winding or tap of the input reactor which provides the gating voltage for the first SCR. The presence of the notch, even though de-emphasized by a waveshaping circuit coupling the gating voltage to the first SCR, creates a negative voltage on and a resulting negative current into the gate of the SCR during conduction. This condition may result in over dissipation and ultimate failure of the gate-cathode junction of the first SCR.